For the adjustment procedure with gases, you need the probe that is going be adjusted, accurate reference gas(es), a pressure regulator, a flow meter, a field check adapter (can be ordered from Vaisala) and flexible tubing with 3 mm (1/8 in) inner diameter. For information on available accessories and ordering, see Spare parts and accessories.
To achieve reliable results, reference gases must be traceable to appropriate standards (for example NIST).
- If adjustment is done by using 1
reference gas (1-point adjustment), the concentration of the gas must be near to the
concentration values in which the device is used.
When adjustment is done only in 1 point, this results in high accuracy only near to the adjustment point, not necessarily over the whole measurement range.
- When using 2 reference gases (2-point adjustment), the reference gas concentrations should represent the low-end and the high-end of the measuring range. The low-end concentration should be less than 20 % of the measuring range of the probe. The 0 gas can be N2 gas with a purity of N5.0 (or better). The high-end gas can be mixture of CO2 and N2 with concentration near to the upper limit of the measuring range, being 110 % of the range at maximum. Accuracy of the concentrations should be 1 % (or better). Difference between the reference gas concentrations should be more than 20 % of the measuring range.